This invention relates to preprinted duplicating masters for producing copies at least by the use of pressure alone.
With the ever increasing work load on teachers and instructors, it becomes important to use modern technology to relieve the teachers of some of the duties ordinarily undertaken. One tool of frequent use by educators is the spirit duplication process for producing copies of tests and instructional materials. Typically, the teacher makes a master copy or master which in turn is used to produce the plural copies.
The master is basically a sheet having reverse-printed thereon an ink composition which when contacted by a copy sheet having at least the surface wet with a solvent or spirit material will transfer a portion of that ink. Thus, plural copies of the master are made by bringing the sheets to be printed into contact with the reverse printed side of the master. U.S. Pat. Nos. 2,748,024 to Klinowski; 2,824,812 to Drautz; and 3,036,924 to Newman are examples of spirit duplicating ink compositions and printing processes.
Initially, the masters were individually made from a transfer sheet having a surface coating of a spirit duplicating material. Using a typewriter, for example, some of the material on the transfer sheet was transferred to a sheet overlying the transfer sheet by striking the overlay sheet and causing the ink to be crash printed on the overlay sheet.
It has been found that it is also possible to preprint masters with ink compositions of the spirit duplicating type. Then the teacher can use such preprinted masters to make copies for students on a given subject without having to compose the assignment itself. But the use of such preprinted masters still requires the use of fluid spirits. In addition, the costs involved in spirit duplicating because of the use of such fluids are higher than a transfer process which is capable of use without fluid.
Also of interest in the background of this invention are the plastic structures which have an ink material dispersed therein and will transfer some of that ink by the application of pressure. Such structures are formed as printing plates, hand stamps, ink rollers for printing processes, and the like, but as far as known have not been used in making preprinted duplicating masters. They generally comprise a synthetic plastic material and an inking material. The plastic acts as an adhesive resinous vehicle; a porous, microreticulated structure; or a binder and retains the inking material until it is exuded under pressure. The plastic structure is usually made by mixing the plastic with a solvent or plasticizer to form a paste, organosol, plastisol or the like and then shaping the plastic and curing by using heat. The inking material can be added to the plastic material before the shaping step or after the porous structure is formed. Examples of such processes and structures are U.S. Pat. Nos. 3,037,879, 3,359,900 and 3,458,339 to Newman; U.S. Pat. No. 3,436,234 to Terry et al; and U.S. Pat. Nos. 2,777,824; 3,055,297 and 3,101,668 to Leeds. Reference is also made to Champion U.S. Pat. No. 2,320,769.